The impact of a particle on a transistor or close to a transistor can result in a stray current in an integrated circuit, according to the ionizing power of this particle for example, characterized by its linear energy transfer (LET). The quantity of charge generated by a particle corresponds to that applied during the change of state of a logic node controlled by a transistor. The consequence of this impact can be the change of state, or of levels, of the logic signals, and consequently lead to errors at the output of the circuit.
Some sectors of business, such as aerospace or the medical sector, need a component robustness that allows for a response reliability close to 100%, this feature taking precedence over all the other factors.
To check the state of the electronic components of an integrated circuit in particular, it is a known practice to perform a test using an automatic test pattern generator, generally referred to by the acronym ATPG. This is done upon leaving the integrated circuit production line, and/or, in certain cases, built-in standalone tests, referred to by the acronym LBIST (Logic Built-In Self-Test) during the operation of the circuit.
An ATPG is a computer-assisted test method used to find an input test sequence which, when it is applied to an integrated circuit, enables a test equipment item external to the integrated circuit to distinguish between a normal behavior and a defective behavior of the electronic circuit being tested. The test sequences generated are used to test semiconductor devices as they leave the production line before they are put in use.
A built-in standalone test method, often referred to by the acronym BIST (Built-In Self-Test), is a mechanism, enabling a hardware or software system, or a system comprising both, to perform its own diagnostic procedure independently. The diagnostic procedure can be initiated automatically, for example, at regular intervals or each time the integrated circuit is started up by triggering a self-monitoring circuit, or even continuously.
This mechanism is often found in integrated circuits, because it allows for checking of the circuit to be automated. This checking is done before the functional check.
The LBIST test is a form of BIST test in which the integrated circuits are configured to be capable of performing their own operation test. This is done without computer assistance or other external equipment.
The LBIST test comprises an advantage of making it possible to test internal electronic circuits that do not have external connection terminals, allowing the circuit to be connected directly to an external automated system such as an ATPG. It also offers the advantage of being able to initiate a test phase at any moment during the life of the integrated circuit.
In an LBIST test, at least one test sequence is injected into the electronic components to be tested. An analysis of the signal is obtained at the output of the components in response to the injected test sequence.
The major drawback is that, when an LBIST test phase is initiated during the operation, the information contained in each of the electronic components is lost. Consequently, the integrated circuit cannot resume its operation following the test precisely in the state in which it was before the test.